Answer: 345;275
Step-by-step explanation:
Lest say v_1 the speed of the slowest plane
v_2 the speed of the fasterst plane
[tex]\Bigg\{\begin{array}{ccc}v_2-v_1&=&70\\4*v_2+4*v_1&=&2480\\\end{array} \right.\\\\\\\Bigg\{\begin{array}{ccc}v_2-v_1&=&70\\v_2+v_1&=&620\\\end{array} \right.\\\\\\\Bigg\{\begin{array}{ccc}2*v_2&=&690\\v_2+v_1&=&620\\\end{array} \right.\\\\\\\Bigg\{\begin{array}{ccc}v_2&=&345\\v_1&=&275\\\end{array} \right.\\\\\\[/tex]
